The invention relates to a process for determining at least one fuel-injection-related parameter for an internal-combustion engine with a common-rail fuel injection system individually for each engine combustion chamber and each injection operation. In particular, the invention relates to a process for determining the fuel quantity injected for each cylinder and per power cycle in an actual manner into the respective combustion chamber without taking the mean value. Specifically, in the case of a separate preinjection and main injection, the process separately determines the preinjection quantity and the main injection quantity of (1) the actual injection point in time, (2) of the actual opening duration of the injectors of the injection system, (3) of the injection points in time of the preinjection and the main injection in the case of a separate preinjection and main injection, (4) of the interval between the preinjection and the main injection and/or (5) of the actual injection pressure at the respective injection nozzle as the one or the several determined fuel-injection-related parameter(s).
From German Patent Document DE 31 26 393 C2 and U.S. Patent Document U.S. Pat. No. 5,176,122 as well as Japanese Published Patent Application JP 08144826 A, it is known to detect the pressure in the distributor pressure space, jointly assigned to the engine combustion chambers, of a common-rail fuel injection system. This is done by means of an assigned pressure sensor. The output signal of the pressure sensor is used for controlling or regulating the fuel injection. In this case, the pressure signal of this sensor is only used at one or a few points of its time sequence per power cycle of an engine combustion chamber, particularly for detecting the differential pressure before and after an injection operation and to determine from the pertaining pressure drop the injected fuel quantity.
This known approach in which only one or a few pressure values of a respective injection operation are used for determining a fuel-injection-related parameter is limited with respect to its achievable precision. The reason is that the output signal of the pressure sensor arranged in the distributor pressure space of the common-rail injection system has a complex course with one pressure break respectively for the fuel injection in each one of the usually several engine combustion chambers, in which case these pressure breaks rapidly follow one another with respect to time and are superimposed by pertaining pressure fluctuation effects and other disturbances. The pressure drop determined by means of two measured pressure values in a starting phase and in an end phase of a fuel injection operation is therefore not always a reliable measurement of the actually injected fuel quantity and other fuel-injection-related parameters.
From European Published Patent Application EP 0 742 361 A2, a process is known for detecting the fuel quantity delivered by an injection pump of a diesel engine and injected by way of injection ducts and assigned injection nozzles into the engine combustion chambers, during which, for the injection ducts, a respective pressure course curve during the delivery operation between the injection pump and the injection nozzles is detected and standardized. Subsequently, the surface integral of the standardized pressure course curve is formed. By an evaluation by means of a proportionality constant, the absolute fuel quantity is then determined from the surface integral.
The invention is based on the technical problem of providing a process of the above-mentioned type by which one or more fuel-injection-related parameter(s) can be determined with low sensor-related expenditures in a comparatively precise and reliable manner.
The invention solves this problem by providing a process for determining at least one fuel-injection-related parameter for an internal-combustion engine with a common-rail fuel injection system individually for each engine combustion chamber and each injection operation. In the case of this process, the pressure in the distributor pressure space, which is assigned jointly to the engine combustion spaces, of the common-rail fuel injection system is detected for a respective fuel injection operation for a respective cylinder not only at one or a few point(s) in time, but rather during its whole course via a pressure sensor of the distributor pressure space in a highly resolved manner. From the detected pressure course, a pertaining pressure course pattern is obtained from which, in turn, the one or more fuel-injection-related parameter(s) is/are determined individually for each combustion chamber and each injection operation. For this purpose, several conventional methods for the pattern recognition and classification can be used, which also include regression methods and discriminant methods. In each case by means of this approach of using the whole pressure course pattern for a respective injection, the pressure course in the distributor pressure space is used during the whole injection operation for determining the fuel-injection-related parameters, whereby a high precision can be achieved without the requirement of a high-cost sensor system for this purpose. On the contrary, the use of a conventional sensor system in the distributor pressure space is sufficient.
In the case of a process further developed according to the present invention, the one or more fuel-injection-related parameter(s) is/are determined by means of the obtained pressure course pattern using a neural network which, in this case, takes over the task of the recognition and analysis of the pressure course pattern. In this case, several functional values of the pressure course pattern are supplied to the neural network as an input vector.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.